This invention relates generally to building construction and more particularly to a roof panel attachment clip for metal roofs on large buildings.
Butler Manufacturing Company, and other manufacturers, specialize in the construction of large metal buildings such as warehouses. The roof on such a building typically comprises a substructure or frame formed from structural beams and metal purlins running between the gables. The purlins and beams support an array of metal panels which are overlapped in the direction perpendicular to the roof ridge. A common way of joining the panels laterally is to preform vertical edge flanges on them, and then roll the mating flanges of adjacent panels together to form a so-called standing seam roof. The connection between the purlins and the metal flanges may be a short vertical strap whose upper end is rolled into the flange. The lower end of the strap may be slidably attached to the clip, which is in turn affixed to the purlin by rivets, bolts or screws.
For all-metal roofs, provision has to be made for thermal expansion and contraction. The substructure temperature remains much more stable than the roof panels, which may undergo large temperature swings as a result of solar heating and changes in ambient air temperature. In a large roof, the cumulative differential expansion may be several inches. Use of high-expansion materials like aluminum aggravates the problem.
In the lateral direction, parallel to the roof ridge, the standing seams act as small expansion loops which accommodate changes in panel width resulting from temperature changes. But as there are no corresponding corrugations in the ridge-wise direction, some provision has to be made in the panel mounting structure. A number of prior patents disclose devices in which the mounting tab, or similar structure, rides in a slot in a bracket as the roof temperature changes.
When installing roofs with slotted brackets, installers are directed to center the tabs in the slots initially. But, should the installer fail to do so, and place the tab at one end of the slot, the tab will not be able to move in one direction. Then, undesirable stress will be placed on the bracket when extreme roof expansion or contraction, as the case may be, occurs. Admonitions may be insufficient to insure uniformly correct installation.